In this instructable, you will learn how to make a digital timer using the old parts of a defective microwave oven. All parts needed in this project can be salvaged from a defective microwave oven. The main thing you need in this project is the microwave oven's timer module.

Step 1: Gather Parts and Tools Needed.


  • Old microwave oven timer (salvaged from an old microwave oven)
  • AC cord and connector (can be salvaged from the old microwave oven)
  • Electrical tape or heat shrink tubing


  • Soldering iron and solder
  • Screwdriver

Step 2: Disassembling the Oven

Warning: Do not attempt do this unless you know about electricity and do not work with the appliance plugged to the mains.

The first thing you need to do is to disassemble the microwave oven. First, take off the cover by removing all screws. You will find several screws after disassembling it. Then, find a screw that holds the timer in place. Next, find a way to take off the timer from its place. You can disconnect or cut some wires if needed. Cut and salvage the wires that supply power to the timer module and disconnect the yellow and black wires from the door switch.

Sorry for the lack of pictures because I needed another hand to do it.

Step 3: Desoldering

Desolder the relays on the board but if you are making an appliance timer, do not desolder it. There are three relays in my board and I desoldered all because I needed the relays for another project. I think you can just leave one relay if you are making the appliance timer.

Step 4: Wiring

Use the salvaged AC connector to power the digital timer module. Strip its ends and tin its tips.

Short the yellow and black wires of the switch so the timer will think that the door is closed.

Connect the power cord to the connector by soldering. After soldering put some heat shrink tubes.

Tip: Slide the heat shrink tubes in before soldering.

Step 5: Testing

Test the timer if it works by connecting the AC connector to the board and then plug it in the wall.

See if there is a display. Don't just leave it bare as I did. You should put an enclosure for your project. Find a way to have an enclosure.

Congratulations! Now you made your own digital timer. You could now use it in the kitchen for timing something.

Thank you for reading! Please comment :)

<p>whats the longest period timed</p>
<p>I managed 99,99minutes, Mine has 2 relays. One does cut off on long timing around 15seconds every minute.the other stays on all the time. I m thinking to change one off the relays to NC so I can turn on something .in a delay of time, instead of turning off.</p>
The timer works. But the relay to my appliance socket is not working. Should I de solder the other two relays? Thanks for your help :) this is my first electronic project.
<p>If one of the relays are not working, I think you should try to transfer the connectors to another relay. You should hear a click as you start the timer.</p>
Could this type of digital timer handle a 1000 watt metal halide bulb? It's for a exposure unit in building. Need to have the light burn the screen for 30 sec and then shut off. Any help would be much appreciated. Thanks :)
<p>It depends on the relay on the module's board. My relay was rated 250V 17A. Multiply voltage and current to get power. V x I = P (250V x 17A = 4250W). For a 1000w bulb, the relay rating must be at least 250V 5A.</p>
<p>I used to do something very similar with either the old clock for a stove, or a timer-operated coffee maker. I make an alarm clock out of the timer for a Mr. Coffee drip coffee maker, and the buzzer out of a dryer. (The buzzer was simply a coil with a &quot;U&quot; shaped spring to both sides of the core.) Guaranteed to make you wake up trying to figure how to shut the sadistic thing off! Microwave oven controllers, usually needed some method of bypassing the door over-ride switch. The relays needn't be removed, as they can be used for various things.. An external socket to turn on an appliance, (Or that sadistic buzzer), and another socket to plug a lamp into, needing only the single &quot;Oven Light&quot; button to turn on/off.</p>
<p>There are two types of a.c. switches in microwaves: a heavy duty triac, and a relay switch. The relay is positive for on/off, the triac however may bleed enough voltage through to keep some items energized even after the timeout event, such as cell phone chargers. I have one in my shop and use it for my soldering sessions, 99.99 minutes max. works out to be just about right for me, if I forget to unplug the iron this will disconnect it for me. Also handy is the timer function itself, great if you're counting slow shaft revolutions to determine r.p.m.'s, epoxy setups, anything else that requires your attention while background timing an event.</p>

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